Glomerular basement membrane (GBM) function is altered in three notable human diseases that affect the kidneys: Goodpasture syndrome/anti-GBM nephritis, Alport syndrome and diabetes mellitus. The molecular defects underlying Goodpasture and Alport syndromes have been linked to type IV collagen, the major constituent of GBM. These advances raise many unanswered questions about the structure, function and role of these chains in the pathogenesis of Goodpasture and Alport syndromes and diabetic renal disease. Understanding structure and assembly of normal type IV collagen is a prerequisite for delineating pathogenic mechanisms. The central thrust of this renewal proposal is to express truncated chains and NC1 domains in eukaryotic cells for elucidation of 1) assembly mechanisms of human type IV collagen suprastructures and 2) pathogenic mechanisms of how mutations in these chains cause defective assembly. The specific aims are: Aim 1: To characterize type IV collagen of normal human GBM with respect to composition, organization and crosslinking of chains. Aim 2: To elucidate discriminatory molecular interactions that code for the assembly of human type IV collagen suprastructures. Aim 3: To elucidate how genetic mutations cause defective assembly of type IV collagen suprastructures. Aim 4: To elucidate the epitope structure for Goodpasture autoantibodies. Aim 5: To sub-localize the epitope for the Alport alloantibodies within the NC1 domain.